Conventionally, there is a pre-filled syringe characterized in that a medical drug is enclosed in the syringe in advance. This pre-filled syringe is easy to use since it allows drugs to be administered as they are without having to perform a drug filling operation. Accordingly, this pre-filled syringe is applied to various drugs and widely used.
In addition to such a type of pre-filled syringe enclosing only a liquid drug, there is also a pre-filled syringe, as disclosed in WO/2005/089837, that has separate chambers partitioned therewithin and enclosing a liquid drug and a powdered drug, respectively, which are in use mixed, dissolved and suspended for administration.
Medical drugs thus stored without being prepared for mixing a liquid drug and a powdered drug are often not suitable to be stored in the prepared state since the drugs may be unstable in the mixed state, and the drugs in contact with moisture for a relatively long period of time may cause defects such as a decrease in titer, deterioration or coagulation of the drugs, which leads to difficulty in distribution of the drugs upon administration.
If a gasket partitioning the internal space into chambers enclosing a liquid drug and a powdered drug, respectively, is highly absorptive, the gasket absorbs the liquid drug (or moisture thereof), to cause the liquid drug to reach the portion corresponding to the wall of the powered drug chamber, with the result that the powdered drug and the liquid drug may be brought into contact with each other. Furthermore, if the powdered drug is unstable to moisture, also when the portion of the gasket corresponding to the wall of the powdered drug chamber is not dry, the powdered drug may come into contact with moisture due to the moisture remaining in the gasket.
In order to solve the problem caused by the moisture contained in the powdered drug chamber, the invention disclosed in Japanese Patent Laying-Open No. 6-142203 is proposed. According to this, for the purpose of preventing the moisture remaining due to sterilization by steam from affecting the powdered drug, the intermediate gasket is formed of two members, and one of the members located closer to the powdered drug chamber is fully dried and inserted after sterilization by steam, thereby preventing moisture from remaining in the powdered drug chamber.